Toyota Sienna Quiz
Supplemental restraint system

Front Occupant Classification Sensor RH Circuit Malfunction

In this manual: Supplemental restraint system
Introduction — 55Service specifications — 7Maintenance — 7Engine — 264U151e automatic transaxle — 108Transfer — 19Propeller shaft — 8Drive shaft — 14Differential — 16Axle — 18Suspension — 37Tire and wheel — 54Brake control — 141Parking brake — 16Steering Column — 11Power steering — 18Air conditioning — 106Supplemental restraint system — 146Seat belt — 22Theft deterrent — 14Engine immobiliser — 17Cruise control — 65Lighting — 61Wiper and washer — 13Door lock — 42Meter — 28Audio / visual — 94Navigation — 108Park assist / monitoring — 33Horn — 5Garage door opener — 42GR-FE Engine control system — 126Supplemental restraint system — 147Other system — 14Windshield / windowglass — 43Mirror — 23Instrument panel — 6Seat belt — 22Seat — 92Engine hood / door — 104Exterior — 39Interior — 5Sliding roof — 9Multiplex communication — 18Can communication — 23
34steps
~204min
4/5difficulty
Done 0 of 34

DTC B1781 Front Occupant Classification Sensor RH Circuit Malfunction

DESCRIPTION

The front occupant classification sensor RH circuit consists of the occupant classification ECU and the front occupant classification sensor RH.

DTC B1781 is recorded when a malfunction is detected in the front occupant classification sensor RH circuit.

DTC No.

DTC Detecting Condition

Trouble Area

B1781
  • The occupant classification ECU receives a line short circuit signal, an open circuit signal, a short circuit to ground signal or a short circuit to B+ signal in the front occupant classification sensor RH circuit for 2 seconds.
  • Front occupant classification sensor RH malfunction
  • Occupant classification ECU malfunction
  • Front seat assembly RH (Front occupant classification sensor RH)
  • Occupant classification ECU
  • Front seat wire RH

WIRING DIAGRAM

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

  • If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see the under surface of the seat cushion.
  • In the above case, hold the seat so that it does not fall down. Holding the seat for a long period of time may cause a problem, such as seat rail deformation. Hold the seat only as necessary.

1 CHECK DTC

  1. Turn the ignition switch to the ON position.
  2. Clear the DTCs stored in the memory.
HINT: First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.
  • Turn the ignition switch to the LOCK position.
  • Turn the ignition switch to the ON position.
  • Check the DTCs (35).

    • OK: DTC B1781 is not output. HINT: Codes other than DTC B1781 may be output at this time, but they are not related to this check.

    USE SIMULATION METHOD TO CHECK

    2 CHECK CONNECTION OF CONNECTORS

    1. Turn the ignition switch to the LOCK position.
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Check that the connectors are properly connected to the occupant classification ECU and the front occupant classification sensor RH.

    OK: The connectors are properly connected.

    CONNECT CONNECTORS, THEN GO TO STEP 1

    3 CHECK FRONT SEAT WIRE RH (SHORT TO B+)

    CHECK FRONT SEAT WIRE RH (SHORT TO B+)
    1. Disconnect the connectors from the occupant classification ECU and the front occupant classification sensor RH.
    2. Connect the negative (-) terminal cable to the battery.
    3. Turn the ignition switch to the ON position.
    4. Measure the voltage according to the value(s) in the table below.

    Standard voltage

    Standard voltage

    REPAIR OR REPLACE FRONT SEAT WIRE RH

    4 CHECK FRONT SEAT WIRE RH (OPEN)

    CHECK FRONT SEAT WIRE RH (OPEN)
    1. Turn the ignition switch to the LOCK position.
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Using a service wire, connect O6-1 (SVC2) and O6-3 (SGD2), and connect O6-2 (SIG2) and O6-3 (SGD2) of connector "C".
    NOTICE: Do not forcibly insert a service wire into the terminals of the connector when connecting.
  • Measure the resistance according to the value(s) in the table below.

    • Standard resistance

    Standard resistance

    REPAIR OR REPLACE FRONT SEAT WIRE RH

    5 CHECK FRONT SEAT WIRE RH (SHORT)

    CHECK FRONT SEAT WIRE RH (SHORT)
    1. Disconnect the service wire from connector "C".
    2. Measure the resistance according to the value(s) in the table below.

    Standard resistance

    Standard resistance

    REPAIR OR REPLACE FRONT SEAT WIRE RH

    6 CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

    CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)
    1. Measure the resistance according to the value(s) in the table below.

    Standard resistance

    Standard resistance

    REPAIR OR REPLACE FRONT SEAT WIRE RH

    7 CHECK DTC

    1. Connect the connectors to the occupant classification ECU and the front occupant classification sensor RH.
    2. Connect the negative (-) terminal cable to the battery.
    3. Turn the ignition switch to the ON position.
    4. Clear the DTCs stored in the memory.
    HINT: First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.
  • Turn the ignition switch to the LOCK position.
  • Turn the ignition switch to the ON position.
  • Check the DTCs (35).

    • OK: DTC B1781 is not output. HINT: Codes other than DTC B1781 may be output at this time, but they are not related to this check.

    USE SIMULATION METHOD TO CHECK

    8 REPLACE OCCUPANT CLASSIFICATION ECU

    1. Turn the ignition switch to the LOCK position.
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Replace the occupant classification ECU.

    HINT: Perform the inspection using parts from a normal vehicle if possible

    9 PERFORM ZERO POINT CALIBRATION

    1. Connect the negative (-) terminal cable to the battery.
    2. Connect the intelligent tester to the DLC3.
    3. Turn the ignition switch to the ON position.
    4. Using the intelligent tester, perform "Zero point calibration" (28).

    OK: "COMPLETED" is displayed

    Go to step 12

    10 PERFORM SENSITIVITY CHECK

    1. Using the intelligent tester, perform "Sensitivity check" (28).

    Standard value: 27 to 33 kg (59.52 to 72.75 lb)

    Go to step 12

    11 CHECK DTC

    1. Turn the ignition switch to the ON position.
    2. Clear the DTCs stored in the memory.
    HINT: First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.
  • Turn the ignition switch to the LOCK position.
  • Turn the ignition switch to the ON position.
  • Check the DTCs (35).

    • OK: DTC B1781 is not output. HINT: Codes other than DTC B1781 may be output at this time, but they are not related to this check

    END

    12 REPLACE FRONT SEAT ASSEMBLY RH

    1. Turn the ignition switch to the LOCK position.
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Replace the front seat assembly RH ( for flat type, SE-48 for manual seat, SE-58 for power seat).

    13 PERFORM ZERO POINT CALIBRATION

    1. Connect the negative (-) terminal cable to the battery.
    2. Connect the intelligent tester to the DLC3.
    3. Turn the ignition switch to the ON position.
    4. Using the intelligent tester, perform "Zero point calibration" (28).

    OK: "COMPLETED" is displayed.

    14 PERFORM SENSITIVITY CHECK

    1. Using the intelligent tester, perform "Sensitivity check" (28).

    Standard value: 27 to 33 kg (59.52 to 72.75 lb)

    END

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